A tri-compartmental, or total, knee joint replacement includes the preparation and resurfacing of the femur, tibia and patella bones. Briefly, the surgical procedure involves calculated bone resections of each bone with the goal of replacing damaged articular cartilage, restoring the joint line and returning the patient to a pain-free movement of the knee joint.
In order to ensure proper knee joint kinematics, trial components of the femur, tibia and patella are used interoperatively. During the surgery, each bone is resected and the trial components are placed on each respective bone to allow the surgeon to trial the joint through a full range of motion. During trialing, the surgeon assesses the joint line, range of motion and ligament tension. Trial components represent various thicknesses, widths, or profiles to replicate the final implant prosthesis. The trialing process allows the surgeon to ensure proper knee joint function prior to the implantation of the final prosthesis.
Patella trials are an example of trialing instruments in preparation for permanent implants. Implants are known to be modular in which they may be stacked to accommodate individual physiological differences between patients, such as is disclosed in U.S. Patent Application Publication No. 2006/0015184A1 to Winterbottom et al., the entirety of which is incorporated herein by reference. Current patella trials are known to use at least a 2-piece design. In accordance with U.S. Pat. No. 6,855,150 to Linehan, the entirety of which is incorporated herein by reference, pegs may extend downwardly from an articular surface member and can be inserted into a drill guide to form a combination patellar trial and drill guide. The patellar trial and drill guide may then be inserted into a resected patella and this assembly may then be placed in a femoral groove and run through a range of motion test. If the patellar trial and drill guide is not the appropriate size or is in the wrong location, a different patellar trial and drill guide may be inserted and retested. This method and the devices used for this method has the option of the patella being drilled for the permanent implant after trialing as the drill guide does not have features that mate with pre-drilled holes in the resected patella. Thus, the trialing in Linehan will not be done with a trial implant having the same shape nor placed in the same location as the final permanent implant.
Furthermore, current patella trial systems are offered as reusable instruments distributed in instrument trays. These trialing systems are expensive to manufacture, clean, sterilize and ship. There is currently an entire patella trial designed to represent each patella implant offering in a knee implant system. The problem thus exists that for every surgery an entire system of patella trials, which may be in kit form, need to be cleaned, sterilized and enter the surgical field in an operating room. This is very expensive, inefficient and increases the risk of infection due to increased instrumentation in the operating room.
There exists a need for a new patella trialing system which maximizes the surgeons interoperative flexibility while minimizing instrument costs, minimizing cleaning/sterilization costs and minimizing the chance of infection.